Modern storage systems, such as XtremIO, support non-disruptive upgrades (NDUs) to allow upgrading a software version without system downtime and without impacting system performance or a user's workload.
Storage systems like XtremIO are very complex and consist of multiple layers of management processes and a layer of datapath processes that intercommunicate and work in synergy in order to maintain high performance and high availability of the system.
During an upgrade all processes need to be restarted with a new software version code, reconfigured, and all connections need to be reestablished without causing hiccups from the host side.